If Congress regulates social networks in new ways following the 2016 election, no single person will have been more responsible than Senator Mark Warner of Virginia. In the aftermath of the election, it was Warner who pushed Silicon Valley executives to delve more deeply into their data, looking for signs of Russian electoral interference.

How much the social networks have cooperated is still on Warner’s mind, however. He believes that there are far more ad purchases and more Russian-linked accounts than the companies have disclosed, and he’s pushing them to search more deeply.

“I said, ‘This doesn’t pass the smell test. You gotta go back and dig in. If this were a new market opportunity, I know the resources you could put into it,’” Warner told me.

The next step of Warner’s investigation will be in two weeks, when executives from Google, Twitter, and Facebook will testify before the Senate Intelligence Committee. The following Q&A details what Warner’s thinking about in the weeks leading up to the hearing.

This interview has been edited and condensed for clarity.

Alexis Madrigal: So, as of today, what do we know about the Russian disinformation campaign on Facebook and other social-media platforms?

Mark Warner: First of all, let’s step back and put the Russian involvement in 2016 in the overall context. It was approved at the highest level. It was coordinated in ways that were unprecedented. It included the things that have been much reported on, like hacking into both political parties and releasing information harmful to one candidate, Clinton, and helpful to Trump.

We know that Russians and even Trump’s Department of Homeland Security have acknowledged that 21 states had their electoral systems probed, if not fully hacked into. We know that this is part of a pattern that has been going on and continues after the election. And it included interventions in the French election, where Facebook was much more active.

I think our government and the platform companies were more than a little bit caught off guard. I don’t think anyone had seen anything of this scale before.

Madrigal: When did you start investigating what happened?

Warner: Right around the time of the election a guy who works for me said, if you Google “election hacking,” you don’t get Fox or MSNBC or CNN. Four of the first five stories were from Russia Today and Sputnik. This was Google, not even Facebook and Twitter. And there were lots of reports of trolls on social media pushing stories. So, it was clear they were using these tools.

I’ve been a supporter of these tech companies from a policy standpoint. But when I started saying that it appears that there were these trolls trying to use these platform companies to interfere in the election, the companies’ initial reaction was that they blew it off. That disappointed me. There was the famous Zuckerberg comment. And into February and March, they were dismissive.

Yet at the same time, coincident with this, there were the Dutch elections and the Dutch ended up hand counting their ballots because they were concerned about potential foreign intervention.

Some of the senior Facebook and social-media companies’ executives came out in the spring and I really pressed them. They started to say they were acknowledging something. Facebook talked about the 30,000 to 50,000 accounts in France that they banned. They said, “We’ve woken up to this.” But it was still many months later, this summer, before any of the companies started to produce some of the content and acknowledge paid advertising and fake accounts. That was just Facebook.

We had experts come in who said, this could very well be targeted on a geographic basis, targeted on demographics. Having been in politics and in the tech business, you look at a 750 percent increase in digital advertising in politics between 2012 and 2016, and you say, if you’re going to try to disrupt an election, you would use digital tools. Because it is a lot easier to target it and it’s the Wild West, there’re no election-advertising rules.

And if you do it right the way, you leave few fingerprints.

Madrigal: In your mind, what are the key outstanding questions?

Warner: All these companies need to come fully clean about what happened in 2016. Don’t tell me they found 450 accounts linked to the American election when they found 50,000 in France. And don’t tell me they found all the ads.

The first pass from Twitter was worse. They took only things that were derivative of what Facebook found. And they found some stuff. But I said, you have to go back and dig in. So, we need to figure out, number one, what happened in 2016.

While I’m trying to not get into the whole editorial-content argument, this notion that we can’t curate at all just doesn’t hold water. They’ve had to do it every time there has been something that has created consequences. Child pornography for example, or terrorist activity, or information on how to create bombs.

A lot of that was forced by the European governments. Areas reach a tipping point, the [platform companies] step in and act. They have to, if you don’t want over-the-top regulation, or worse yet, we allow this to continue and we have some massive upheaval or loss of faith in the democratic process. Because people see how bad this was with relatively small amounts of dollars spent.

Madrigal: How might this translate into legislation?

Warner: Where we’re headed with legislation is the lightest touch possible. Keep some residual location where someone can go look at the [political-advertising] content. Basically apply some of the most basic rules that apply to print and broadcasting to digital media. It doesn’t get at the whole problem, but it gets at the question of tagging political advertising.

There is not a legislative proposal here, but I think there is going to be a growing interest in this topic. What I want to make sure is clear to the American people, this is not as simple as following the money on Russian ads. We need to look at the bots on Twitter and the pages on Facebook. Has this been done in collaboration with hate groups in the United States? Is it reinforcing the hate groups? How much responsibility do the companies have to sort through all that?

Madrigal: Facebook executives, publicly and privately, as well as pundits like Mark Penn, have argued that any Russian interference had a negligible effect because it was too small-time within the scale of Facebook. Are they right?

Warner: If this tiny tip of the iceberg is the extent of the activity, that might hold some water. But if there is, which I suspect, a much bigger piece of the iceberg below, then they are wrong. The numbers are much, much larger. The public press, so far, is really looking at what is still a limited universe.

You can target very discrete demographic locales. There still remains a question: How did they know where to target? I don’t have an answer yet. I don’t know if we’ve got the full evidence. Some people suspect this was very targeted in Wisconsin and Michigan where the Democrats were asleep at the switch. How were they smarter than the Democrats? That may not be a high hurdle to get over.

Madrigal: You represent a lot of non–Silicon Valley tech companies in Virginia. How have they reacted to the pressure you’ve been putting on Facebook, Google, Twitter, and others?

Warner: I’ve been surprised that they have been so generally supportive of me driving the whole investigation to its conclusion. The fact that we’ve kept it bipartisan is extraordinarily important. There is not a week that goes by that I don’t get more worried about our vulnerabilities, in my work on this or the banking committee or looking at Equifax.

Since we’re a high-defense state, it’s not always the best thing to say, but if you take all the Russians spent in messing with our election, the French elections, Dutch elections, and all double it, you’re still less than the cost of one F-35.

As someone who comes from a pro-defense state, we have to ask: Do we have the best military money can buy, when we’re seeing the first attacks made in 21st-century digital conflict? I would not narrow it to just the Russian electoral interference. I would talk about the Chinese OPM breach, Chinese intellectual-property stealing around stealth. This is such an asymmetrical area. Our technology advantages end up being a disadvantage.

We have been reluctant as a nation to respond too much. You start a cyber conflict when we are so technology-dependent, who knows where it ends?

The one thing that is absolutely clear: We don’t have a whole-government approach to cyber. Yahoo has a 500 million user breach. How’s that not material enough to report it in your [Securities and Exchange Commission] filings? We have 49 different cyber-breach laws in 49 states. They didn’t need to disclose it.

Madrigal: You mentioned driving this investigation “to its conclusion.” What might that look like?

Warner: Let’s make sure we know entirely what happened. Let’s try to figure out specifically: Was there collaboration or collusion? And in terms of the social-media companies and platform companies, let’s get all the facts of how extensive this interference was. What happened in 2016 happened. We need to know the extent of it to protect our elections. And I don’t think there is any indication that what was happening during the election stopped on November 8.

Going forward, let’s have at least regulations on transparency on spending and the ability to look at the content of political advertisements. And in a way that’s not too heavy-handed and maintains the freedom of the internet, let’s at least start the discussion about information integrity, so that Americans know that if they see somewhere that Mark Warner is saying something bad about Donald Trump, you have some faith that it actually is real.